c# - Cell styles in OpenXML spreadsheet (SpreadsheetML)

Question

I've generated a .xlsx spreadsheet in C# using the OpenXML SDK, but can't figure out how to get cell styles working. I've been studying files produced by Excel, and can't quite figure out how it's done.

Right now, I'm creating a fill, creating a CellStyleFormat that points at the fill, creating a CellFormat that points at the index of the CellStyleFormat, then creating a CellStyle that points to the CellFormat.

Here's the code I'm using to generate the document:

Console.WriteLine("Creating document");
using (var spreadsheet = SpreadsheetDocument.Create("output.xlsx", SpreadsheetDocumentType.Workbook))
{
    Console.WriteLine("Creating workbook");
    spreadsheet.AddWorkbookPart();
    spreadsheet.WorkbookPart.Workbook = new Workbook();
    Console.WriteLine("Creating worksheet");
    var wsPart = spreadsheet.WorkbookPart.AddNewPart<WorksheetPart>();
    wsPart.Worksheet = new Worksheet();

    var stylesPart = spreadsheet.WorkbookPart.AddNewPart<WorkbookStylesPart>();
    stylesPart.Stylesheet = new Stylesheet();
    stylesPart.Stylesheet.Fills = new Fills();

    // create a solid red fill
    var solidRed = new PatternFill() { PatternType = PatternValues.Solid };
    solidRed.AppendChild(new BackgroundColor { Rgb = HexBinaryValue.FromString("FF00FF00") });

    stylesPart.Stylesheet.Fills.AppendChild(new Fill { PatternFill = new PatternFill() { PatternType = PatternValues.None } });
    stylesPart.Stylesheet.Fills.AppendChild(new Fill { PatternFill = solidRed });
    stylesPart.Stylesheet.CellStyleFormats = new CellStyleFormats();
    stylesPart.Stylesheet.CellStyleFormats.AppendChild(new CellFormat { FillId = 0, ApplyFill = false });
    stylesPart.Stylesheet.CellStyleFormats.AppendChild(new CellFormat { FillId = 1, ApplyFill = true });
    stylesPart.Stylesheet.CellFormats = new CellFormats();
    stylesPart.Stylesheet.CellFormats.AppendChild(new CellFormat { FormatId = 0 });
    stylesPart.Stylesheet.CellFormats.AppendChild(new CellFormat { FormatId = 1 });
    stylesPart.Stylesheet.CellStyles = new CellStyles();
    stylesPart.Stylesheet.CellStyles.AppendChild(new CellStyle { Name = "None", FormatId = 0 });
    stylesPart.Stylesheet.CellStyles.AppendChild(new CellStyle { Name = "Solid Red", FormatId = 1 });

    stylesPart.Stylesheet.Save();

    Console.WriteLine("Creating sheet data");
    var sheetData = wsPart.Worksheet.AppendChild(new SheetData());

    Console.WriteLine("Adding rows / cells...");

    var row = sheetData.AppendChild(new Row());
    row.AppendChild(new Cell() { CellValue = new CellValue("This"),  DataType = CellValues.String });
    row.AppendChild(new Cell() { CellValue = new CellValue("is"),    DataType = CellValues.String });
    row.AppendChild(new Cell() { CellValue = new CellValue("a"),     DataType = CellValues.String });
    row.AppendChild(new Cell() { CellValue = new CellValue("test."), DataType = CellValues.String });

    sheetData.AppendChild(new Row());

    row = sheetData.AppendChild(new Row());
    row.AppendChild(new Cell() { CellValue = new CellValue("Value:"),   DataType = CellValues.String });
    row.AppendChild(new Cell() { CellValue = new CellValue("123"),      DataType = CellValues.Number });
    row.AppendChild(new Cell() { CellValue = new CellValue("Formula:"), DataType = CellValues.String });
    row.AppendChild(new Cell() { CellFormula = new CellFormula("B3"),   StyleIndex = 1 }); // 

    Console.WriteLine("Saving worksheet");
    wsPart.Worksheet.Save();

    Console.WriteLine("Creating sheet list");
    var sheets = spreadsheet.WorkbookPart.Workbook.AppendChild(new Sheets());
    sheets.AppendChild(new Sheet() { Id = spreadsheet.WorkbookPart.GetIdOfPart(wsPart), SheetId = 1, Name = "Test" });

    Console.WriteLine("Saving workbook");
    spreadsheet.WorkbookPart.Workbook.Save();

    Console.WriteLine("Done.");
}

Here's the generated XML:

workbook.xml

<?xml version="1.0" encoding="utf-8"?>
<x:workbook xmlns:x="http://schemas.openxmlformats.org/spreadsheetml/2006/main">
  <x:sheets>
    <x:sheet name="Test" sheetId="1" r:id="Rbad86b8c80844a16" xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships" />
  </x:sheets>
</x:workbook>

styles.xml

<?xml version="1.0" encoding="utf-8"?>
<x:styleSheet xmlns:x="http://schemas.openxmlformats.org/spreadsheetml/2006/main">
  <x:fills>
    <x:fill>
      <x:patternFill patternType="none" />
    </x:fill>
    <x:fill>
      <x:patternFill patternType="solid">
        <x:bgColor rgb="FF00FF00" />
      </x:patternFill>
    </x:fill>
  </x:fills>
  <x:cellStyleXfs>
    <x:xf fillId="0" applyFill="0" />
    <x:xf fillId="1" applyFill="1" />
  </x:cellStyleXfs>
  <x:cellXfs>
    <x:xf xfId="0" />
    <x:xf xfId="1" />
  </x:cellXfs>
  <x:cellStyles>
    <x:cellStyle name="None" xfId="0" />
    <x:cellStyle name="Solid Red" xfId="1" />
  </x:cellStyles>
</x:styleSheet>

worksheets/sheet.xml

<?xml version="1.0" encoding="utf-8"?>
<x:worksheet xmlns:x="http://schemas.openxmlformats.org/spreadsheetml/2006/main">
  <x:sheetData>
    <x:row>
      <x:c t="str"><x:v>This</x:v></x:c>
      <x:c t="str"><x:v>is</x:v></x:c>
      <x:c t="str"><x:v>a</x:v></x:c>
      <x:c t="str"><x:v>test.</x:v></x:c>
    </x:row>
    <x:row />
    <x:row>
      <x:c t="str"><x:v>Value:</x:v></x:c>
      <x:c t="n"><x:v>123</x:v></x:c>
      <x:c t="str"><x:v>Formula:</x:v></x:c>
      <x:c s="1"><x:f>B3</x:f></x:c>
    </x:row>
  </x:sheetData>
</x:worksheet>

The last cell of the last row is where I'm trying to add the style.

This all validates properly when I run it through the OpenXML SDK Productivity Tool, but, when I attempt to open the file in Excel, I get the following error:

Repaired Records: Format from /xl/styles.xml part (Styles)

The spreadsheet then shows, but the fill isn't applied.

Any idea how to go about fixing this?

Answer 1

Right, I managed to figure this out, after a lot of experimentation.

It turns out that excel reserves styles 0 and 1 for normal cells and "Gray125" pattern fill respectively. Most of the above code can be removed, as we only need a CellFormat really.

Working code:

Console.WriteLine("Creating document");
using (var spreadsheet = SpreadsheetDocument.Create("output.xlsx", SpreadsheetDocumentType.Workbook))
{
    Console.WriteLine("Creating workbook");
    spreadsheet.AddWorkbookPart();
    spreadsheet.WorkbookPart.Workbook = new Workbook();
    Console.WriteLine("Creating worksheet");
    var wsPart = spreadsheet.WorkbookPart.AddNewPart<WorksheetPart>();
    wsPart.Worksheet = new Worksheet();

    var stylesPart = spreadsheet.WorkbookPart.AddNewPart<WorkbookStylesPart>();
    stylesPart.Stylesheet = new Stylesheet();

    Console.WriteLine("Creating styles");

    // blank font list
    stylesPart.Stylesheet.Fonts = new Fonts();
    stylesPart.Stylesheet.Fonts.Count = 1;
    stylesPart.Stylesheet.Fonts.AppendChild(new Font());

    // create fills
    stylesPart.Stylesheet.Fills = new Fills();

    // create a solid red fill
    var solidRed = new PatternFill() { PatternType = PatternValues.Solid };
    solidRed.ForegroundColor = new ForegroundColor { Rgb = HexBinaryValue.FromString("FFFF0000") }; // red fill
    solidRed.BackgroundColor = new BackgroundColor { Indexed = 64 };

    stylesPart.Stylesheet.Fills.AppendChild(new Fill { PatternFill = new PatternFill { PatternType = PatternValues.None } }); // required, reserved by Excel
    stylesPart.Stylesheet.Fills.AppendChild(new Fill { PatternFill = new PatternFill { PatternType = PatternValues.Gray125 } }); // required, reserved by Excel
    stylesPart.Stylesheet.Fills.AppendChild(new Fill { PatternFill = solidRed });
    stylesPart.Stylesheet.Fills.Count = 3;

    // blank border list
    stylesPart.Stylesheet.Borders = new Borders();
    stylesPart.Stylesheet.Borders.Count = 1;
    stylesPart.Stylesheet.Borders.AppendChild(new Border());

    // blank cell format list
    stylesPart.Stylesheet.CellStyleFormats = new CellStyleFormats();
    stylesPart.Stylesheet.CellStyleFormats.Count = 1;
    stylesPart.Stylesheet.CellStyleFormats.AppendChild(new CellFormat());

    // cell format list
    stylesPart.Stylesheet.CellFormats = new CellFormats();
    // empty one for index 0, seems to be required
    stylesPart.Stylesheet.CellFormats.AppendChild(new CellFormat());
    // cell format references style format 0, font 0, border 0, fill 2 and applies the fill
    stylesPart.Stylesheet.CellFormats.AppendChild(new CellFormat { FormatId = 0, FontId = 0, BorderId = 0, FillId = 2, ApplyFill = true }).AppendChild(new Alignment { Horizontal = HorizontalAlignmentValues.Center });
    stylesPart.Stylesheet.CellFormats.Count = 2;

    stylesPart.Stylesheet.Save();

    Console.WriteLine("Creating sheet data");
    var sheetData = wsPart.Worksheet.AppendChild(new SheetData());

    Console.WriteLine("Adding rows / cells...");

    var row = sheetData.AppendChild(new Row());
    row.AppendChild(new Cell() { CellValue = new CellValue("This"),  DataType = CellValues.String });
    row.AppendChild(new Cell() { CellValue = new CellValue("is"),    DataType = CellValues.String });
    row.AppendChild(new Cell() { CellValue = new CellValue("a"),     DataType = CellValues.String });
    row.AppendChild(new Cell() { CellValue = new CellValue("test."), DataType = CellValues.String });

    sheetData.AppendChild(new Row());

    row = sheetData.AppendChild(new Row());
    row.AppendChild(new Cell() { CellValue = new CellValue("Value:"),   DataType = CellValues.String });
    row.AppendChild(new Cell() { CellValue = new CellValue("123"),      DataType = CellValues.Number });
    row.AppendChild(new Cell() { CellValue = new CellValue("Formula:"), DataType = CellValues.String });
    // style index = 1, i.e. point at our fill format
    row.AppendChild(new Cell() { CellFormula = new CellFormula("B3"),   DataType = CellValues.Number, StyleIndex = 1 });

    Console.WriteLine("Saving worksheet");
    wsPart.Worksheet.Save();

    Console.WriteLine("Creating sheet list");
    var sheets = spreadsheet.WorkbookPart.Workbook.AppendChild(new Sheets());
    sheets.AppendChild(new Sheet() { Id = spreadsheet.WorkbookPart.GetIdOfPart(wsPart), SheetId = 1, Name = "Test" });

    Console.WriteLine("Saving workbook");
    spreadsheet.WorkbookPart.Workbook.Save();

    Console.WriteLine("Done.");
}

---

Some advice:

Use ClosedXML if you want to avoid this insanity.

I cannot recommend ClosedXML highly enough if you're doing this kind of work. The OpenXML API and format is horribly tedious to work with on its own, with all sorts of undocumented cases. ClosedXML does so much of the leg work for you. They're also really great at getting bugs fixed quickly.